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The magic of GPS
Read more on - Polity | Economy | Schemes | S&T | Environment
- Building block of modern life: Imagine modern life without the Global Positioning System (GPS)! Whether guiding drivers around unfamiliar roads, helping runners keep track of the miles they rack up around their local park or simply pointing to a lost set of keys, GPS has become an essential, invisible layer in our everyday lives.
- GPS depends on: The technology relies on a constellation of satellites that orbit the Earth and transmit radio signals towards the planet’s surface. By picking up the signals from several satellites at once, a receiver on the ground can calculate their position on Earth, precise to a few metres. The ideas behind GPS took several decades and many billions of dollars to develop. No surprise, then, that it was a project of the American military as a way to keep track of their most important assets around the globe. Only an institution like that could realistically have afforded or justified building it.
- Accident begets widespread adoption: The technology became available to civilians in 1983 after a South Korean passenger jet inadvertently strayed into prohibited Soviet airspace and was shot down, killing all 269 passengers on board. The American government realised that if positioning technology had been available to the pilot of the airliner, the tragedy might have been averted.
- Evolution: Modern military satellites can do much more than find your location. By bouncing radio waves off the surface of the Earth, some systems can build up extremely detailed pictures of what is going on there—some are reportedly even capable of detecting enemy submarines by measuring the tiny disturbances left by their wakes in the curvature of the ocean surface. And you are probably by now familiar with the high-resolution pictures and video that satellites record for reconnaissance or to guide missiles. Until now, most of these technologies have remained within armed forces or wrapped up in secretive intelligence agencies. A big part of that has been down to cost—building a satellite and launching it into space are eye-wateringly expensive.
- Small sateliltes arrive: It changed in recent years. A new generation of small satellites that can be built and launched cheaply are bringing to civilians capabilities that were once the preserve of governments alone. The latest is the ability to listen in (from space) on the faint radio signals used by ships in order to navigate or send messages to each other. Why would anyone—beyond the usual cadre of spies and soldiers—want to do this? For one thing, it turns out to be a useful way to spot illegal fishing.
- Stealing fish: The law of the sea requires fishing vessels to carry GPS-based automatic identification systems (AIS) that broadcast where they are at all times. In mid-2020, however, Ecuadorians watched with concern as 340 foreign boats entered their waters near the Galapagos Islands. Many of the boats had their AIS systems switched off, which provoked worries that they were sneaking into Ecuador’s waters to steal fish. Everyone concerned denied having done anything wrong but radio-signal monitoring, by a cluster of shoebox-sized satellites launched by HawkEye 360, a private company, confirmed the infractions into Ecuador’s economic zone.
- Useful application: It is easy to see how cheap, widely available satellite systems such as this could be used for routine maritime surveillance—not only to protect economic interests but also to prevent damage to marine protected zones or to keep ports secure.
- Knowledge centre -
- Triangulation and trilateration - Trilateration is a method of surveying in which the lengths of the sides of a triangle are measured, usually by electronic means, and, from this information, angles are computed. Triangulation is a surveying method that measures the angles in a triangle formed by three survey control points. Using trigonometry and the measured length of just one side, the other distances in the triangle are calculated. While trilateration relies on signal strength as an analog for distance, triangulation relies on timing differences in the reception of tags' signals. Because these signals travel at the speed of light, the time differences in transmission are very small. This makes measuring instruments more expensive. As GPS satellites broadcast their location and time, trilateration measure distances to pinpoint their exact position on Earth. While surveyors use triangulation to measure distant points, GPS positioning does not involve any angles whatsoever.
- Starlink by SpaceX - Starlink is a satellite internet constellation being constructed by Elon Musk's SpaceX, providing satellite Internet access. The constellation will consist of thousands of mass-produced small satellites in low Earth orbit (LEO), working in combination with ground transceivers. As of 12 March 2021, SpaceX had launched 1,265 Starlink satellites (including demo satellites Tintin A and B). They plan to launch up to 60 more per Falcon 9 flight, with launches as often as every two weeks in 2021. In total, nearly 12,000 satellites are planned to be deployed, with a possible later extension to 42,000.
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